1. Technical Field
The present invention relates to an electro-optical device using an electro-optical material such as liquid crystal, and more particularly to a technique for protecting circuits of the electro-optical device from overvoltage.
2. Related Art
In electro-optical devices such as liquid crystal devices, a plurality of pixels arranged on a substrate is driven by various signals supplied from input terminals arranged along the circumference of the substrate via wiring lines. For example, image signals (for example, signals having signal levels according to gray levels to be displayed) supplied from the input terminals via image signal lines are sampled by a sampling circuit and are supplied to the pixels. With this configuration, there may be a case where a sudden overvoltage (a pulse having a differential waveform, such as a spike or surge) due to static electricity occurring in the input terminals is applied to the wiring lines. Such an overvoltage may cause a damage to parts of the electro-optical device, such as switching elements composing the sampling circuit. To overcome this problem, there has been proposed a technique of suppressing the overvoltage using electrostatic protection circuits connected to wiring lines. In this case, the electrostatic protection circuits are arranged to be connected to portions branched from the wiring lines when viewed from the direction perpendicular to a substrate. However, for such an arrangement where the electrostatic protection circuits are spaced apart from the wiring lines, there is a need to secure an additional space for forming the electrostatic protection circuits separately from a space for forming the wiring lines. On this account, there may arise a problem in that it is difficult to reduce the size of a region (a so-called frame) surrounding a display region. Particularly, when the number of wiring lines is increased in order to obtain high-definition display images, this problem becomes more serious since the space in which the electrostatic protection circuits of the wiring lines are arranged is forced to be enlarged.